Two of every kind of land animal entered the ark, including those animals (for example, dinosaurs) that have become extinct in the millennia following the Flood. The animals were all young animals, since they would have to spend the year in the ark without reproducing and then emerge to repopulate the earth after the Flood. The animals entering the ark possessed genes for the remarkable physiologic abilities of migration and hibernation. These were not needed in the equable climates of the primeval world, but would be vital for survival in the post-Flood world. After being installed in their respective "rooms" in the ark, and after a good meal, most of them probably spent most of the Flood year in a state of hibernation.